.TH std::experimental::disjunction 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::experimental::disjunction \- std::experimental::disjunction

.SH Synopsis
   Defined in header <experimental/type_traits>
   template< class... B >                        (library fundamentals TS v2)
   struct disjunction;

   Forms the logical disjunction of the type traits B..., effectively performing a
   logical or on the sequence of traits.

   The specialization std::experimental::disjunction<B1, ..., BN> has a public and
   unambiguous base that is

     * if sizeof...(B) == 0, std::false_type; otherwise
     * the first type Bi in B1, ..., BN for which bool(Bi::value) == true, or BN if
       there is no such type.

   The member names of the base class, other than disjunction and operator=, are not
   hidden and are unambiguously available in disjunction.

   Disjunction is short-circuiting: if there is a template type argument Bi with
   bool(Bi::value) != false, then instantiating disjunction<B1, ..., BN>::value does
   not require the instantiation of Bj::value for j > i.

.SH Template parameters

   B... - every template argument Bi for which Bi::value is instantiated must be usable
          as a base class and define member value that is convertible to bool

   Helper variable template

   template< class... B >
   constexpr bool disjunction_v =                          (library fundamentals TS v2)
   disjunction<B...>::value;

.SH Possible implementation

   template<class...> struct disjunction : std::false_type {};
   template<class B1> struct disjunction<B1> : B1 {};
   template<class B1, class... Bn>
   struct disjunction<B1, Bn...>
       : std::conditional_t<bool(B1::value), B1, disjunction<Bn...>>  {};

.SH Notes

   A specialization of disjunction does not necessarily inherit from of either
   std::true_type or std::false_type: it simply inherits from the first B whose
   ::value, explicitly converted to bool, is true, or from the very last B when all of
   them convert to false. For example, disjunction<std::integral_constant<int, 2>,
   std::integral_constant<int, 4>>::value is 2.

.SH Example

    This section is incomplete
    Reason: no example

.SH See also

   disjunction variadic logical OR metafunction
   \fI(C++17)\fP     \fI(class template)\fP

.SH Category:
     * Todo no example
